Non-insulin-dependent diabetes mellitus (NIDDM) is more prevalent in Japanese Americans than in native Japanese or the general U.S. White population. In a series of ongoing studies, our goal has been to study longitudinally in Japanese Americans the development of abnormal glucose tolerance in relation to risk factors associated with the insulin resistance syndrome. This is our general hypothesis: The high prevalence of NIDDM in Japanese Americans results from the effects of environmental (behavioral) factors reflecting "westernization". The latter include nutrition, physical activity, acculturation, and psychosocial stress. The result is an increased prevalence of insulin resistance, hyperinsulinemia, hyperglycemia, and weight gain with preferential truncal fat deposition leading to NIDDM (the insulin resistance syndrome). Our specific aim for the intervention research in this proposal is: To demonstrate that increased endurance type physical activity and a reduction of dietary animal (saturated) fat by Japanese Americans with IGT will result in a reduction of risk factors associated with progression to NIDDM. We will examine in 80 Japanese Americans with IGT (40 men and 40 women) baseline and follow-up (6 and 24 mo) body composition, body fat distribution (including visceral fat), insulin sensitivity, and beta cell function, as well as selected lipid and lipoprotein measurements associated with the insulin resistance syndrome.